Everquest was the fist MMO I played extensively. My first characters were created on the Innoruk server and it took several tries to find a class that worked for me. The first time I played I spent most of my time on a gnome cleric. I ended up with a cleric because that was the class that was always in the most demand and it made it relatively easy to find groups. Although the name of the game was 'Everquest' there were actually very few quests in the game, they offered very little reward and in order to find them you had to 'hail' and speak to NPC's until you found one that said something interesting. NPC interaction was very odd. They would say something and then you could try saying something back to them by typing it in. If you managed to hit a properly constructed keyword or phrase the NPC would offer more information.
The most prevalent mode of game play in EQ is camping. Camping is the practice of selecting a spot where the main party waits while the designated 'puller' goes out and brings monsters back for the group to kill. The primary motivation for camping was to avoid adds. An add is a monster that attacks the party in addition to the one being currently fought. Camps are placed in areas that are known to be safe where no monster will wander through or come close enough to aggro on the party. Another reason for camping is monsters have fixed spawn locations and a chance of dropping high value items that can be obtained nowhere else. This makes some monsters or camps (places where those monsters can be killed) highly desirable. So desirable that there will nearly always be a group 'camping the spawn'. It was common practice when I was playing for a player to shout "Camp Check" or "CC" when they first entered an area to find out what spots were taken and to get in line to join when a spot opened up. Once a group was in position it was not uncommon for them to remain for 6, 8, or even 12 hours at a stretch trying to acquire a single item. More than once I joined groups where people claimed to have spent 24 hours or more at the same location killing the exact same monsters over and over again every time they spawned.
Another unique aspect of playing Everquest was trains. Not mechanical locomotives but long parades of monsters chasing a player or group of players. Trains arise from a combination of factors. The first thing required for a train is for a player or group to aggro more monsters than they can handle. Once the monsters start attacking a player they will not stop until either the player is dead or leaves the region by zoning out (crossing a line where the server removes them from the current area and loads them into the next). A monster will aggro on every player that it comes near making the train dangerous not only to the person being chased but to everyone it runs past as well. If a skeleton is chasing Brutus to the zone line and they pass nearby, as soon as Brutus zones out or dies that skeleton, and every other monster they pass on the way, is going to come after you.
Imagine if you will a typical zone being camped and farmed. The area is a long series of tunnels and interconnected rooms filled with monsters. At various locations throughout the dungeon there are groups of players in their camp spots killing the things that spawn nearby. Now, Deep in the bowels of this dungeon a group is fighting the most difficult and dangerous enemies when something goes wrong. Maybe the tank dies or the healer disconnects, but whatever happens, suddenly the group is running for the exit in an attempt to avoid death. But they are far, far down in the dungeon and it is such a very long run to the exit. As they flee they run past other monsters who start to chase them and through other player camps which causes those groups to collapse and flee as well bringing yet more monsters behind them. This is a train, and like a train wreck it causes massive amounts of destruction as it careens through the dungeon until everyone in its path is dead or gone.
What I have described is not an uncommon occurrence. Players normally shout "Train" or give some other warning to let others know what is coming and give them a chance to get to safety. Trains can also be used by unscrupulous players to intentionally kill others. If someone has pissed you off or you want to dislodge a group from your favorite camping spot it is possible to 'train' them and get them killed. Several classes can do this but none so easily as the monk. The monk can run through a group of monsters while you are busy fighting something else and then charge into the middle of your group. Once the monsters that are chasing him arrive he will feign death causing all the monsters to stop attacking him and turn on you instead. Then once things calm down he can get up and walk away. To add insult to injury Everquest does not have (or did not the last I played) any restriction on who can loot a corpse. If you left unlooted monsters behind when you fled or died the monk can get up, take whatever was left on the corpses, and get cleanly away.
The main reason I stopped playing Everquest wasn't because of player griefing as it was with UO but because the game play is the perfect definition of grinding. People literally sit in the exact same spot for hours at a time killing the exact same monsters over and over repeatedly in order to move their experience bar a tiny fraction further towards the next level. Advancement is so slow in Everquest that the game has two experience bars. The first bar shows the progress towards the next level and the gauge is broken down into several small 'bubbles'. The second bar shows only progression through the current bubble and in a typical play session a mid to high level player would expect only that the second bar make modest progress toward being filled. Also whenever a player dies in Everquest they loose experience and can even loose a level in addition to leaving all their items on their corpse where they died.
At some point when my character was in the mid 40's (and the level cap was still 50) I suddenly suffered a disconnect between the game world and the game mechanics. No longer was I an adventurer killing monsters. Instead I was a person sitting at a keyboard watching a progress bar advance pixel by agonizing pixel. The degree of repetition and tedium became overwhelming and I could no longer bear to do the things that were needed to advance. I continued to play for a little while longer exploring the game world and visiting dungeons I had never been to before but I was unable to make any progress or see many of the areas because I couldn't do it alone and the vast majority of players were focused entirely on doing what was needed to safely advance rather than going into unfamiliar places where they would almost certainly be killed.